<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>

        .compat .flex-container {
            height: 400px;
            display: flex;
            flex-direction: column;
        }

        .compat .full-other-height {
            flex: 1;
            overflow: auto;
        }


    </style>

</head>
<body class="compat">

<div class="flex-container">

    <div>abc</div>
    <div class="full-other-height">
        <div style="height: 100%;">
            <div style="height: 500px"></div>

        </div>
    </div>
</div>
abc

</body>
</html>